Light pipes are elongated monofilament or single fiber optic cables of relatively large diameter that are capable of transmitting light from one end to the other. Light pipes may either be "end-fire" light pipes, meaning that they are constructed to transmit light longitudinally with minimal lateral or radial light emission, or "side-fire" light pipes that are configured to both transmit light longitudinally and emit light laterally. Light pipes may include no more than a simple core of a clear plastic material, or may include one or more of a number of different claddings and coatings. End-fire light pipes may include jackets including claddings configured to prevent lateral light emissions. Side-fire light pipes may include claddings configured to encourage or diffuse such lateral emissions. These claddings may be flouropolymer tubes applied by such methods as heat shrinking the tube onto the core or inserting a core into a pre-formed cladding tube by pressure filling. Some light pipe jackets also include a clear or translucent plastic coating that surrounds and protects the cladding.
Light pipes are most commonly circular in cross section, but have also been formed in a number of other cross-sectional shapes. For example, U.S. Pat. No. 5,218,660 issued Jun. 8, 1993 to Omata discloses a light pipe having a polygonal cross-section. U.S. Pat. No. 4,734,829, issued Mar. 29, 1988 to Wu et al., discloses an arc lamp image transformer that includes a light pipe having the same arcuate cross-sectional shape as the beam of light it will transmit. U.S. Pat. Nos. 4,668,264 and 4,669,814 issued May 26, 1987 and Jun. 2, 1987, respectively, to Dyott, each disclose light pipes having a non-circular, e.g., half-circular, cross-sections each defining two transverse orthogonal axes. U.S. Pat. No. 5,221,387, issued Jun. 22, 1993 to Robbins et al. and assigned to Lumenyte International Corporation (the Lumenyte '387 patent) suggests that alternate cross-sectional light pipe shapes including squares, triangles and various fluted shapes might be used.
It is desirable to suspend or otherwise support light pipes in positions where they can transmit light from a source to a desired point and/or to illuminate a desired area. Some suspension systems disclosed in the prior art include rings or clips that encircle or partially encircle the light pipes they suspend. The rings or clips are affixed in some way to a supporting structure in a light fixture. Such suspension systems do not require modifications to the light pipes they are designed to suspend.
Other light pipe suspension systems include structures that integrally extend from some portion of a light pipe and that are configured to engage an adjacent support structure. For example, the Lumenyte '387 patent discloses a light pipe having a cross-sectional shape that includes a tangentially oriented elongated mounting protrusion included in an outer coating of the light pipe. The outer coating surrounds a cladding layer that surrounds a core of the light pipe. The protrusion extends the entire length of the light pipe and functions to aid in mounting the conduit to a backing, wall or other support structure. The mounting protrusion is extruded simultaneously with the coating in a co-extrusion process that forms the light pipe.
Another example of a light pipe suspension system that relies on an appendage extending from the light pipe is the system disclosed in U.S. patent application Ser. No. 08/767,969. The application is assigned to the assignee of the present application and discloses a light pipe having an elongated integral appendage extending radially outward from along the length of the light pipe and having a "Christmas tree"-shaped cross section. The "branches" of the tree are configured to engage opposed edges of an elongated mounting slot. Light pipes having integral appendages of this type have relatively complex cross-sectional shapes.
What is needed is a simple, cost-effective light pipe suspension system that includes a light pipe configured to mount easily to a supporting structure while being inexpensive to manufacture.